1. Field of the Invention
The present invention relates to a golf club head designed to stabilize the direction of a hit ball and carry the hit ball further. The present invention also relates to a set of iron clubs having such golf club heads.
2. Discussion of Prior Art
Generally, a head main body of an iron club is formed of metal such as soft iron, stainless steel or the like to have integral hosel, sole and face portions. The head main body of the golf club head varies in shape according to the iron club numbers. It is widely known that a recessed portion is formed on the back side of the head main body with the peripheral edge portion thereof remaining unrecessed as it is, to increase the moment of inertia of the head main body and stabilize the direction of the hit ball.
In view of tile above fact, in recent years, there have been proposed several kinds of iron clubs. For example, according to an iron club which is shown in FIGS. 22 and 23, in the ball hitting surface of a head main body 1 formed of metal, there are formed a through hole 2 and a fitting recessed portion 3 in the peripheral edge portion of the through hole 2, and also a thin face plate 4 having elasticity is fitted into the fitting recessed portion 3 to thereby form a recessed portion 6 in the back portion 5 of the head main body 1 (see Japanese Utility Model Publication No. 55-277 of Showa). Also, according to an iron club which is shown in FIG. 24, in the back portion 8 of a head main body 7, there is formed a recessed portion 9, with the peripheral portion thereof remaining unrecessed as it is, to thereby form a thin ball hitting surface 11 in the face portion of the head main body 7.
In other words, according to the above iron clubs, since the recessed portions 6, 9 are formed in the back portions 5, 8 with the peripheral edge portions remaining untreated, the weights of the head main bodies 1, 7 are dispersed around the peripheral edge portions thereof, thereby being able to increase the moments of inertia of the head main bodies 1, 7 and thus to stabilize the direction of the hit ball.
On the other hand, however, since the recessed portion 6 is formed in the back portion 5 of the head main body 1 by fitting the thin face plate 7 into the through hole 2 formed in the head main body 1, or, since the thin ball hitting surface 11 is formed in the face portion 10 by forming the recessed portion 9 in the back portion 8, the above-mentioned iron clubs lack in surface rigidity when hitting the ball and thus there is a possibility that the face plate 7 and the ball hitting surface 11 can be broken, or, the lack of surface rigidity makes it impossible to extend the carry of the hit ball.
Also, in Japanese Utility Model Publication No. 59-12914 of Showa, there is disclosed an iron club set in which, as shown in FIGS. 25 to 27, not only a recessed portion 14 is formed in the back portion 13 of a head main body 12 with the peripheral edge portion thereof remaining unrecessed, and a rib-shaped heavy weight portion 15 is so provided in the recessed portion 14 as to extend from the top side peripheral edge portion to the sole side peripheral edge portion, but also the heavy weight portion 15 is gradually moved in position according to the kinds of iron clubs, that is, as the iron clubs vary in the order of a long iron club 16 shown in FIG. 25, a middle iron club 17 shown in FIG. 26 and a short iron club 18 shown in FIG. 27, the position of the heavy weight portion 15 is moved from a position near the toe portion of the head main body to a position near the heel portion thereof.
Therefore, according to the respective iron clubs, the heavy weight portion 15 keeps the head main body 12 in a proper inclination to thereby be able to prevent the ball from being hooked or sliced.
In the above-mentioned iron club, however, since the heavy weight portion 15 is so formed as to have the same thickness (height) as the peripheral edge portion on the back side of the head main body 12, the weight of the iron club is heavy.
Therefore, in tile above-mentioned head main body 12, in spite of the fact that the recessed portion 14 is formed on the back portion 13 with the peripheral edge portion thereof remaining unrecessed, the weight of the head main body 12 is not dispersed to the peripheral edge portion thereof and thus the moment of inertia is reduced, with the result that the flying direction of the hit ball cannot be stabilized.
In addition, it is not clear whether the heavy weight portion 15 is disposed at a position of the back portion 13 corresponding to the sweet spot (in the present invention, the sweet spot corresponding position means a position in which a perpendicular line drawn from the sweet spot of the face portion of the head main body intersects the back portion of the head main body), and thus the heavy weight portion 15 is not helpful so much in enhancing the surface rigidity of the sweet spot of the ball hitting surface. For this reason, in fact, it cannot be expected that the carry of the hit ball can be extended.
Also, it is generally known that, in a golf club set of this kind, if the center of gravity of a head main body of a long iron is lowered, then the hit ball can be flown high and thus the carry of the hit ball can be extended; and, if the center of gravity of a head main body is moved upwardly as the number of iron clubs increases, then the direction of the head (face) can be intentionally changed and thus the direction of the hit ball can be controlled easily. However, in the golf club set shown in FIGS. 25 to 27, although the right and left direction of the hit ball is considered, that is, prevention of the hooked or sliced ball is considered, in fact, no consideration is given to the adjustment of the center of gravity of the head main body 1.
Therefore, not only the surface rigidity of the sweet spot cannot be expected, but also the carry of the hit ball cannot be secured by the long iron 16 shown in FIG. 25 and the direction of the hit ball still remains difficult to control when using the middle iron 17 and the short iron 18 shown in FIGS. 26 and 27.